Accidentally this whole post in another thread...

Maybe worthy to note, that there was another big church nearby, consecrated to Saint Peter and Paul, which doesn't exist anymore. The town had eleven churches in the middle ages.

Historical sources have a couple of words to say about the burial of Saint Stephen. His two legends, and the legend written by bishop Hartvik says he was laid to rest in the basilica consecrated to Virgin Mary, he founded in the town of Alba (fehérvár = white castle). Hartvik also notes two things: 1. his body was put into a carved marble sarcophagus at the center of the church; 2. his grave was below the level of the floor, covered by large marble slab, and they had to go down to his "coffin", apparently here he uses the words sarcophagus and "tumba", sometimes interchangeably, and from the text they figure the coffin itself might have been put together from stone slabs. Archaeological excavation in the 1970's proved that there was a facility partially below ground level in the middle of the basilica, essentially a crypt, with stairs leading down there, and which was changed during the centuries.
The sarcophagus' - which I posted earlier and widely knows as Saint Stephen's - origin is actually quite foggy. There is data, that in the 19th century it was used as trough for animals, other data says it was found in undisturbed ground. It do has a hole on one end however supporting the its use as a trough. The place of origin is also debated. Contemporary scholars either don't know, or state various places, among them Óbuda (now part of Budapest). The material is limestone (not marble), from local quarry (local as Hungarian, near from Budapest). The first time the idea raised that it was Saint Stephen's coffin was in 1930. Since then all the supporting points was debated, and indeed refuted. Btw the top cover is missing.
One info they cite so many times it's a cliche now, that it's a Roman a modified sarcophagus. I'm not sure where this comes from and I only see this as a statement, and read no supporting evidence or reasoning. Only three sides has decoration (two long and one short), which means it stood by a wall. The style has contemporary parallels in Hungary, and shows analogy with North Adriatic findings, both on the Italian and the Dalmatian sides. Some think it was a work of a Venetian craftsmen hired and invited to the court.
Also some think it was the coffin made for the son of Saint Stephen: Saint Emeric.